EFFECTS OF PARAMETERS VARIATION ON WIND POWER GENERATION

Presentation on EFFECTS OF PARAMETERS VARIATION ON WIND POWER GENERATION
Objectives

1. To analysis the effects of different parameters variation on wind power generation
2. To analysis the Cp vs. λ curve of wind turbine model
3. To observe the 2D and 3D view of Cp vs. λ curve for different wind turbine model.

Output power equation of wind turbine
Output power, P=0.5ρAV³C_p
Where,
ρ= Air density, kg/m³
A=Rotor swept area, m²
V=Wind velocity, m/s
C_p=Power co-efficient
Cp vs. λ equation
Cp = 0.5 (116/λ_i -0.4α -5) e^-21/λi
Where,
λ_i = {1/ (λ+0.08 α) -0.035/ (α³+1)}^-1
λ = ω_m R / υ
λ =Tip speed ratio
α = Blade angle
Factors affecting the wind power generation

1. The windiness of the site
2. Availability
3. Seasonal and diurnal variation of wind power
4. Effect of height
5. Wind velocity variation with time
6. Wind turbine arrangement

Considered parameters

1. Wind velocity (V)
2. Turbine swept area (A)
3. Air density(ρ)
4. Power coefficient (C_p)

Wind velocity

1. Wind velocity has a cubic relation with wind power generation
2. Wind speed varies for different reasons-

height,
season,
day night effect etc.

Three design speed

1. Cut in speed, V_c = (0.6 to 0.7) V_m
2. Rated speed, V_r =(1.5 to2.0) V_m
3. Furling (Cut off) speed, V_f =≥3 V_m

Swept area

1. The swept area of wind turbine’s blades is a function of rotor diameter.
2. The power output of a wind turbine is directly related to the swept area.
3. If double the swept area, the amount of energy which can capture by the wind turbine will be double.

Air density

1. Air density is one of the factors that affects the wind turbine power generation.
2. Air density is effected by-

Temperature
Pressure
Elevation

Power coefficient (c_p)

1. Power coefficient (Cp) is the percentage of power available in the wind that is converted into mechanical power.
2. It is a function of blade angle (α), and the tip-speed-ratio, (λ).
3. Maximum value of Cp is 0.593 but wind turbine rotors achieve values 0.4 to 0.5 due to different loss.

Simulation model

Cp vs. λ (TSR) curve for different blade angle (α) for V52 model

3D view of power coefficient (Cp) for V52 model

Swept area variation for V52 model

Air density variation for V52 model

Aerodynamic power variation as a function of (Cp) for V52 model

Cp vs. λ curve for different blade angle (α) for V80 model

3D view of power coefficient (Cp) for V80 model

Swept area variation for V80 model

Air density variation for V80 model

Aerodynamic power variation as a function of (Cp) for V80 model

Cp vs. λ curve for different blade angle (α) for V90 model

3D view of power coefficient (Cp) for V90 model
 
Swept area variation for V90 model
 
Air density variation for V90 model

Aerodynamic power variation as a function of (Cp) for V90 model
 Conclusion

1. From the Simulation result it can be seen that the output power is directly related to wind speed ,swept area, air density and C_p.
2. Output power mainly affected by the swept area.
3. Output power of same wind turbine varies due to change in air density but it has a small effect.
4. Output power is a function C_p
5. C_p is a function of blade angle & tip speed ratio.
6. C_p is maximum when blade angle is minimum.

Submitted BY SHARMIN SHAMS FERDAUSI and JAHAN ARA ARJU

IMPLEMENTATION OF A VERTICAL AXIS WIND TURBINE

Presentation on IMPLEMENTATION OF A VERTICAL AXIS WIND TURBINE

RENEWABLE ENERGY

RENEWABLE ENERGY IS ENERGY GENERATED FROM NATURAL RESOURCES—SUCH AS SUNLIGHT, WIND, TIDES, AND GEOTHERMAL HEAT—WHICH ARE RENEWABLE. NOW A DAYS RENEWABLE ENERGY IS ONE OF THE MOST IMPORTANT TOPIC IN POWER GENERATION.

ADVANTAGES OF RENEWABLE ENERGY

1. We can use it repeatedly without depleting it.
2. No contribution to global warming.
3. No polluting emissions.
4. Low cost applications when counting all costs.
5. Saving on health and its costs.

RENEWABLE ENERGIES

1. KNOWN RENEWABLE ENERGIES ARE
2. SOLAR
3. WIND
4. BIOMASS
5. HYDRO etc…

TYPES OF WIND TURBINES
Horizontal axis
Turbines that rotate around a horizontal axis are more common. Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and are usually pointed into the wind
Vertical axis
Vertical-axis turbines rotate on a vertical axis.
VERTICAL AXIS
Vertical-axis turbines rotate on a vertical axis. Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. Key advantages of this arrangement are that the turbine does not need to be pointed into the wind to be effective. This is an advantage on sites where the wind direction is highly variable. VAWTs can utilize winds from varying directions.
VAWT SUBTYPES

1. DARRIEUS WIND TURBINE
2. GIROMILL
3. SAVONIUS WIND TURBINE

ADVANTAGES

1. A MASSIVE TOWER STRUCTURE IS LESS FREQUENTLY USED.
2. THEY HAVE LOWER WIND STARTUP SPEEDS THAN HAWTS.
3. THEY MAY BE BUILT AT LOCATIONS WHERE TALLER STRUCTURES ARE PROHIBITED.
4. VAWTS SITUATED CLOSE TO THE GROUND CAN TAKE ADVANTAGE OF LOCATIONS.
5. THEY MAY HAVE A LOWER NOISE SIGNATURE.
6. SIMPLE MANTAINENCE.
7. SIMPLICITY OF MANUFACTURE AND INSTALATION.
8. DOES NOT DEPEND ON WIND DIRECTION

VAWT DISADVANTAGES

1. MOST PRODUCE ENERGY AT ONLY 50% OF THE EFFICIENCY OF HAWTS IN LARGE PART BECAUSE OF THE ADDITIONAL DRAG THAT THEY HAVE AS THEIR BLADES ROTATE INTO THE WIND.
2. A VAWT THAT USES TO HOLD IT IN PLACE PUTS STRESS ON THE BOTTOM BEARING AS ALL THE WEIGHT OF THE ROTOR IS ON THE BEARING.
3. HAVING ROTORS LOCATED CLOSE TO THE GROUND WHERE WIND SPEEDS ARE LOWER DUE TO WIND SHEAR, THEY MAY NOT PRODUCE AS MUCH ENERGY AT A GIVEN SITE AS A HAWT WITH THE SAME FOOTPRINT OR HEIGHT.

DARRIEUS WIND TURBINE
FOR IMPLEMENTING PURPOSE WE CHOOSE THE DARRIEUS TYPE VERTICAL AXIS WIND TURBINE. THE REASONS BEHIND IT ARE GIVEN BELOW.
DARRIEUS TURBINES, WHICH ARE LIFT-DRIVEN, HAVE A HIGHER POWER POTENTIAL THAN THE HORIZONTAL, OR DRAG-DRIVEN TURBINES. THE MAIN DRAWBACK WITH THEIR DESIGN IS THEIR INABILITY TO SELF-START. DARRIEUS TURBINES REQUIRE AN EXTERNAL ENERGY SOURCE TO BRING THE DEVICE TO A MINIMUM ROTATIONAL SPEED
COMPONENTS
Base: The base will be a truncated pyramid, about 3ft tall. This base was made by angles. It has different levels, one at ground level, one hold the way up and one at the top. There is two bearing mounted in the top and bottom of the top levels.

Shaft: Sitting in these bearings will be the shaft. The shaft is a 9ft tall length of steel mechanical tubing, with initial dimensions of 1” in the main part, 0.75” at bottom.
Blades: The dimensions of the blades are 20inch in length and 10inch in wide. Eight prototype blades were made to connect to the turbine. The blades were connected to the turbine body by two nuts at the bottom and the top.

Turbine structure : Attached to the shaft by set screws are 2 circle of steel bar which. These were fabricated at the workshop. The circles are joined to the shaft by two small circles.

GENERATOR
IN THIS DESIGN WE USED A PERMANENT MAGNET DC MOTOR. IT WAS REQUIRED TO USE SYNCHRONOUS GENERATOR BUT WE USED PARMANENT MAGNET MOTOR BECAUSE IT IS AVAILABLE IN THE LOCAL MARKET.

FINAL SETUP

WIND POWER CALCULATION
WIND POWER, P = 0.5 X RHO X A X V³
WHERE,
P = POWER IN WATTS
RHO = AIR DENSITY (ABOUT 1.225 KG/M³ AT SEA LEVEL, LESS HIGHER UP)
A = ROTOR SWEPT AREA, EXPOSED TO THE WIND (M²)
V = WIND SPEED IN METERS/SEC
WIND TURBINE POWER
P = 0.5 x rho x A x Cp x V³ x Ng x Nb
Where,
P = power in watts.
rho = air density.
A = rotor swept area, exposed to the wind (m²)
Cp = Coefficient of performance
V = wind speed in meters/sec
Ng = generator efficiency
Nb = gearbox/bearings efficiency.
WIND SPEED VS. TURBINE POWER

FUTURE IMPROVEMENTS
While the prototype did not perform as well as initially hoped, with a few changes to the design this should improve greatly:

1. The most important area of improvement is the turbine body construction, which could have been done by aluminum.
2. The blades are not perfectly shaped by making the blades perfectly shaped the efficiency of the turbine can be improved
3. Change that would improve the performance is altering the design of the arms.
4. Some of these improvements would be to purchase better bearings, install better bearing support, and add weatherproofing. A better bearing would enable the turbine to turn more freely; reducing the starting torque and making everything work much more smoothly

Submitted by SAYEDUR RAHMAN and SAQUIB SHARIF

Wind turbine modeling using pitch controller

Presentation on Wind turbine modeling using pitch controller

OBJECTIVES

1. Modeling of a wind turbine where pitch angle is a control variable.
2. At the high wind speed the pitch controller will automatically active to maintain the output power at the rated level.

PITCH ANGLE AS A CONTROL VARIABLE

1. The amount of energy that is extracted from wind and converted into mechanical energy is depending on the radial force acting on the blade. The formation of the force depends on particular profile design and dimension.
2. The Cp (λ, β) characteristic gives us a power coefficient, that depends on the tip speed ratio λ and the pitch angle β .
3. For blade profiles two forces are generally used to describe the characteristics, lift force component (F_LIFT ) and a drag component (F_DRAG) which resulting as F_TOTAL.
4. The F_LIFT component and a F_DRAG together are transformed into a pair of axial F_THRUST force and rotor's directions F_TORQUE components, where only the F_TORQUE produces the driving torque around the rotor shaft. By varying the pitch angle, β the size the direction of F_TOTAL components can be changed.
5. The axial forces F_THRUST has no driving effect but puts stress on rotor blades and furthermore, leads to a thrust on the nacelle and on tower.

AERODYNAMIC FORCES AND VELOCITIES AT ROTOR BLADE

POWER COEFFICIENT VS TIP SPEED RATIO CURVE WITH DIFFERENT VALUE OF PITCH ANGLE

Power coefficient surface

Where,

Lamda = Tip speed ratio

Beta = Pitch angle

Cp = Rotor power coefficient

NEED OF PITCH CONTROLLER

1. Because of the fluctuating nature of the wind speed the output of the wind turbine varies.
2. At the high wind speed, fatigue damage can be occurred to the mechanical parts of the wind turbine.
3. By controlling the pitch angle the output power can be limited as the wind turbine rotor power coefficient decreases with the increase of pitch angle.
4. At the high wind speed the automatically activated pitch controller keep the output power within rated level by increasing the value of pitch angle.

BLOCK DIAGRAM

Wind turbine scheme with pitch controller

BLOCK DIAGRAM

Pitch actuator system

OPERATIONAL WAVE SHAPE

MATHMATICAL EXPRESSIONS

The mechanical output power equation is given by,

And the expression for power coefficient is given by,

Where,

MODEL SPECIFICATIONS

The specifications of the wind turbine VESTAS-V52 are given in the following table.

Rotor diameter	52m
Area swept	2124m2
No of blades	3
Power regulation	Pitch/opti speed
Air brake	Full blade pitch
Cut-in wind speed	4m/s
Nominal wind speed	16m/s
Cut-out wind speed	25m/s
Nominal output	850kw

METHODOLOGY

SIMULINK BLOCK OF WIND TURBINE MODEL FOR VESTAS V52

SIMULINK MODEL OF PI CONTROLLER

SIMULINK MODEL OF PITCH ACTUATOR

SIMULATION RESULT

The simulation results obtained from the MATLAB/SIMULINK wind turbine model are given below(for various wind speed)

Wind speed(m/s)	Pitch angle (degree)	Cp	Power(pu)
16(rated)	0	0.1595	1
17	6.22	0.1138	1
19	12.98	0.11	1

RESULT ANALYSIS

From simulation result, we observed that, at rated wind speed pitch angle is zero i.e. pitch controller remains inactive and above rated wind speed the pitch controller is activated and keep the output power at rated value by changing the value of pitch angle.

By using pitch controller the output power has been limited at high wind speed and wind turbine can operate safely. The simulation results has been shown that at the wind speed above the rated speed of the turbine the pitch controller automatically activate and limiting the output power by increasing the pitch angle.

Submitted by- Sudipta Dey and Md. Mazedul Huq